Lyme disease, due to the tick borne spirochete Borrelia burgdorferI (Bb), is a major emerging infection. It was originally recognized in children, and children continue to have a high rate of infection. Major issues concerning neurologic aspects of the disease in children and adolescents remain unresolved. Failure to understand the full spectrum of neurologic features has led to health care practices which may be both costly and ineffective. The objective of this proposal is to characterize the neurologic, cognitive, and behavioral aspects of pediatric disseminated Lyme disease. Three groups of children will be evaluated in a prospective longitudinal 18 month study. Case Group 1 [N=50] will meet Centers for Disease Control and Prevention (CDC) surveillance criteria for neurologic Lyme disease. Case Group 2 [N=50] will meet the CDC surveillance criteria for extraneural Lyme disease [Lyme arthritis, carditis or multifocal erythema migrans. Control Group 3 [N=50] will be composed of an age- sex- and IQ- matched group of healthy Bb seronegative controls. All three groups will have comprehensive neurologic, neuropsychologic, behavioral. and psychosocial evaluations at entry. Subjects with neurologic involvement will have cerebrospinal fluid [CSF] studies. Disseminated Lyme disease subjects will receive currently recommended antibiotic treatment. All three groups will be followed prospectively with full re-evaluation at 18 months. SPECIFIC AIM 1: To delineate the neurologic and CSF features of disseminated Lyme disease in children. Hypothesis 1: Neurologic involvement is common in pediatric disseminated Lyme disease. SPECIFIC AIM 2: To delineate the behavioral and neurocognitive features of disseminated Lyme disease in children. Hypothesis 2: Behavioral changes [dysphoria, irritability, fatigue] and cognitive problems [deficits of attention and memory] are frequent in children with neurologic Lyme disease. These problems will have remitted by 18 month follow up. SPECIFIC AIM 3: To identify specific risk factors for persistent post treatment behavioral and neurocognitive complaints. Hypothesis 3: Persistent post-treatment complaints at the 18 month follow-up are more common in children with psychosomatic problems, and those with parents who reinforce illness-related behavior. This project will: (A) establish the relative frequency, severity, and progression of neurologic and neurobehavioral disturbances associated with pediatric Lyme disease; (B) provide needed data to optimize diagnosis, evaluation, and management of neurologic Lyme syndromes in children. thereby helping to standardize care and reduce medical costs; (C) increase our understanding of underlying pathophysiologic mechanisms of this disorder.